Real Work

I was recently asked to revisit the Road Transport - Future Directions" Study of 1990/91 to see if there was any guidance on energy performance to be extracted from the published results.

In the table following, "demand sat" is the range of outcomes of three land use/transport pricing scenarios for Sydney in the year 2016 - give or take a bit - which adopted a "demand satisfaction" approach to transport demand. "Demand mgt" is the range of outcomes of five scenarios which adopted a "demand management" approach.

Here is part of my findings ...

"Another measure of energy effectiveness could be a comparison of total movement quantity with payload movement quantity. The payload is of course people, who are encased in vehicles of various sizes. Some vehicles (in the case of public transport) may continue circulating around the city at times though nearly empty. If we assume that :

• the average person weighs 75kg
• the average car weighs 1,500kg empty
• the average bus weighs 14,000kg empty
• the average train weighs 400,000kg empty

then calculation based on [results published in 1991] yields the ratios shown in Table 7. The high "mass overhead" of trains is offset by their more energy-efficient operating environment - rolling on rails, using reticulated electricity, precise - though not necessarily accurate - scheduling, signalised control of all sections, gentle grades, large radii, few intersections, no mixed use and hence hardly any requirements for varying speed between stations.

I note that many of these advantages could also be given to non-rail and/or lower-mass systems. Rail rights of way would make perfect cycleways !

Table 7 shows the energy benefits of more intensive use of buses and trains, public transport, and the energy inelasticity of private transport (because more people bring more cars with them)."

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